Channels definition:

#+begin_src shell
guix describe --format='channels' > guix-env/channels.scm
#+end_src

Manifest:

#+begin_src scheme :tangle guix-env/manifest.scm :mkdirp yes
(specifications->manifest
 '("guile"
   "guile-fibers"
   "guile-json"
   "guile-fslib"))
#+end_src

Bash script for activating the environment:

#+NAME: environment_activation_shell_script
#+begin_src shell :tangle guix-env/env.bash :mkdirp yes
#!/usr/bin/env bash

set -Eeuxo pipefail

DIR=$(dirname "$(readlink -f "${0}")")

guix time-machine \
     --channels="${DIR}/channels.scm" -- \
     environment \
     --manifest="${DIR}/manifest.scm"
#+end_src
